Speaker
Mehmet Yilmaz
Title
Passive Full-Wave MOSFET Rectifiers for Electromagnetic Harvesting
Abstract
A new generation of electronic devices has emerged requiring micro-watt-level power supply to operate. Thanks to micro-power processors and sensors, micro-power sources have become an attractive option for industry and research.
This
work
is
interested
in
micro-power
sources
that
harvest
vibrational
energy
by
deploying
electrostatic,
electromagnetic,
and
piezoelectric
transduction
techniques.
The
output
power
of
vibrational
energy
harvesters
is
in
AC
form,
whereas
electronic
loads
require
known
DC
power
supply
to
operate.
Thus,
there
is
a
need
for
AC-DC
conversion
between
harvesters
and
electronic
loads
to
get
DC
power
out
of
AC.
Traditional
full-wave
bridge
rectifiers
and
center-tapped
transformer
rectifiers
are
not
feasible
in
micro-watt-level
harvesters.
Low
output
power
undermines
the
power
efficiency
of
those
traditional
rectifiers.
Thus,
novel,
low
power,
high
efficiency
conversion
circuits
are
required
instead
of
traditional
rectifiers.
This
goal
is
particularly
challenging
when
it
comes
to
electromagnetic
energy
harvesters
since
their
output
voltage
is
much
lower
than
that
of
electrostatic
and
piezoelectric
harvesters.
In
this
work,
we
studied
four
different
full-wave
rectifiers;
a
silicon
diode
bridge
rectifier,
a
Schottky
diode
bridge
rectifier,
a
passive
MOSFET
rectifier,
and
an
active
MOSFET
rectifier.
Out
of
simulation
results,
we
found
the
voltage
and
power
efficiency
of
each
rectifier.
We
found
that
MOSFET-type
rectifiers
are
better
than
diode
type
rectifiers
in
terms
of
voltage
and
power
efficiency.
Both
full-wave
MOSFET
rectifiers
have
about
99%
voltage
and
power
efficiency.
There
is
only
a
small
difference
in
power
and
voltage
efficiency
between
the
two
MOSFET
rectifier
types
below
600mV
input
voltage
amplitude.
Since
active
MOSFET
rectifier
has
extra
components
and
need
of
external
DC
supply
to
power
its
active
devices,
we
concluded
it
was
not
good
option
for
small
scale
harvester
systems.
We
implemented
the
passive
MOSFET
rectifier,
tested
its
performance
in
rectifying
the
output
of
an
electromagnetic
harvester,
and
analyzed
its
effects
on
the
harvester
performance.
When
we
connected
the
MOSFET
rectifier
to
the
harvester
it
doubled
the
optimum
load
resistance
from
24
Ohm
to
48
Ohm.
We
also
studied
the
rectifier
effect
on
harvester's
natural
frequency,
and
it
does
not
change
much
the
natural
frequency
which
means
our
rectifier
acts
like
resistance,
and
we
also
calculated
the
power
efficiency
based
on
harvester
test
and
we
have
maximum
74%
power
efficiency.
Supervisors
Professors Ramadan El-Shatshat, Baris Fidan, Mustafa Yavuz